/*
 * jcprepct.c
 *
 * Copyright (C) 1994, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the compression preprocessing controller.
 * This controller manages the color conversion, downsampling,
 * and edge expansion steps.
 *
 * Most of the complexity here is associated with buffering input rows
 * as required by the downsampler.  See the comments at the head of
 * jcsample.c for the downsampler's needs.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* At present, jcsample.c can request context rows only for smoothing.
 * In the future, we might also need context rows for CCIR601 sampling
 * or other more-complex downsampling procedures.  The code to support
 * context rows should be compiled only if needed.
 */
#ifdef INPUT_SMOOTHING_SUPPORTED
#define CONTEXT_ROWS_SUPPORTED
#endif


/*
 * For the simple (no-context-row) case, we just need to buffer one
 * row group's worth of pixels for the downsampling step.  At the bottom of
 * the image, we pad to a full row group by replicating the last pixel row.
 * The downsampler's last output row is then replicated if needed to pad
 * out to a full iMCU row.
 *
 * When providing context rows, we must buffer three row groups' worth of
 * pixels.  Three row groups are physically allocated, but the row pointer
 * arrays are made five row groups high, with the extra pointers above and
 * below "wrapping around" to point to the last and first real row groups.
 * This allows the downsampler to access the proper context rows.
 * At the top and bottom of the image, we create dummy context rows by
 * copying the first or last real pixel row.  This copying could be avoided
 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
 * trouble on the compression side.
 */


/* Private buffer controller object */

typedef struct {
    struct jpeg_c_prep_controller pub;/* public fields */

    /* Downsampling input buffer.  This buffer holds color-converted data
     * until we have enough to do a downsample step.
     */
    JSAMPARRAY color_buf[MAX_COMPONENTS];

    JDIMENSION rows_to_go;  /* counts rows remaining in source image */
    int        next_buf_row; /* index of next row to store in color_buf */

#ifdef CONTEXT_ROWS_SUPPORTED   /* only needed for context case */
    int this_row_group;     /* starting row index of group to process */
    int next_buf_stop;      /* downsample when we reach this index */
#endif
} my_prep_controller;

typedef my_prep_controller * my_prep_ptr;


/*
 * Initialize for a processing pass.
 */

METHODDEF void
start_pass_prep( j_compress_ptr cinfo, J_BUF_MODE pass_mode ) {
    my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

    if ( pass_mode != JBUF_PASS_THRU ) {
        ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
    }

    /* Initialize total-height counter for detecting bottom of image */
    prep->rows_to_go = cinfo->image_height;
    /* Mark the conversion buffer empty */
    prep->next_buf_row = 0;
#ifdef CONTEXT_ROWS_SUPPORTED
    /* Preset additional state variables for context mode.
     * These aren't used in non-context mode, so we needn't test which mode.
     */
    prep->this_row_group = 0;
    /* Set next_buf_stop to stop after two row groups have been read in. */
    prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
#endif
}


/*
 * Expand an image vertically from height input_rows to height output_rows,
 * by duplicating the bottom row.
 */

LOCAL void
expand_bottom_edge( JSAMPARRAY image_data, JDIMENSION num_cols,
                    int input_rows, int output_rows ) {
    register int row;

    for ( row = input_rows; row < output_rows; row++ ) {
        jcopy_sample_rows( image_data, input_rows - 1, image_data, row,
                           1, num_cols );
    }
}


/*
 * Process some data in the simple no-context case.
 *
 * Preprocessor output data is counted in "row groups".  A row group
 * is defined to be v_samp_factor sample rows of each component.
 * Downsampling will produce this much data from each max_v_samp_factor
 * input rows.
 */

METHODDEF void
pre_process_data( j_compress_ptr cinfo,
                  JSAMPARRAY input_buf, JDIMENSION * in_row_ctr,
                  JDIMENSION in_rows_avail,
                  JSAMPIMAGE output_buf, JDIMENSION * out_row_group_ctr,
                  JDIMENSION out_row_groups_avail ) {
    my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
    int numrows, ci;
    JDIMENSION inrows;
    jpeg_component_info * compptr;

    while ( *in_row_ctr < in_rows_avail &&
            *out_row_group_ctr < out_row_groups_avail ) {
        /* Do color conversion to fill the conversion buffer. */
        inrows = in_rows_avail - *in_row_ctr;
        numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
        numrows = (int) MIN( (JDIMENSION) numrows, inrows );
        ( *cinfo->cconvert->color_convert )( cinfo, input_buf + *in_row_ctr,
                                             prep->color_buf,
                                             (JDIMENSION) prep->next_buf_row,
                                             numrows );
        *in_row_ctr += numrows;
        prep->next_buf_row += numrows;
        prep->rows_to_go -= numrows;
        /* If at bottom of image, pad to fill the conversion buffer. */
        if ( ( prep->rows_to_go == 0 ) &&
            ( prep->next_buf_row < cinfo->max_v_samp_factor ) ) {
            for ( ci = 0; ci < cinfo->num_components; ci++ ) {
                expand_bottom_edge( prep->color_buf[ci], cinfo->image_width,
                                    prep->next_buf_row, cinfo->max_v_samp_factor );
            }
            prep->next_buf_row = cinfo->max_v_samp_factor;
        }
        /* If we've filled the conversion buffer, empty it. */
        if ( prep->next_buf_row == cinfo->max_v_samp_factor ) {
            ( *cinfo->downsample->downsample )( cinfo,
                                                prep->color_buf, (JDIMENSION) 0,
                                                output_buf, *out_row_group_ctr );
            prep->next_buf_row = 0;
            ( *out_row_group_ctr )++;
        }
        /* If at bottom of image, pad the output to a full iMCU height.
         * Note we assume the caller is providing a one-iMCU-height output buffer!
         */
        if ( ( prep->rows_to_go == 0 ) &&
            ( *out_row_group_ctr < out_row_groups_avail ) ) {
            for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                  ci++, compptr++ ) {
                expand_bottom_edge( output_buf[ci],
                                   compptr->width_in_blocks * DCTSIZE,
                                   (int) ( *out_row_group_ctr * compptr->v_samp_factor ),
                                   (int) ( out_row_groups_avail * compptr->v_samp_factor ) );
            }
            *out_row_group_ctr = out_row_groups_avail;
            break;      /* can exit outer loop without test */
        }
    }
}


#ifdef CONTEXT_ROWS_SUPPORTED

/*
 * Process some data in the context case.
 */

METHODDEF void
pre_process_context( j_compress_ptr cinfo,
                     JSAMPARRAY input_buf, JDIMENSION * in_row_ctr,
                     JDIMENSION in_rows_avail,
                     JSAMPIMAGE output_buf, JDIMENSION * out_row_group_ctr,
                     JDIMENSION out_row_groups_avail ) {
    my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
    int numrows, ci;
    int buf_height = cinfo->max_v_samp_factor * 3;
    JDIMENSION inrows;
    jpeg_component_info * compptr;

    while ( *out_row_group_ctr < out_row_groups_avail ) {
        if ( *in_row_ctr < in_rows_avail ) {
            /* Do color conversion to fill the conversion buffer. */
            inrows = in_rows_avail - *in_row_ctr;
            numrows = prep->next_buf_stop - prep->next_buf_row;
            numrows = (int) MIN( (JDIMENSION) numrows, inrows );
            ( *cinfo->cconvert->color_convert )( cinfo, input_buf + *in_row_ctr,
                                                 prep->color_buf,
                                                 (JDIMENSION) prep->next_buf_row,
                                                 numrows );
            /* Pad at top of image, if first time through */
            if ( prep->rows_to_go == cinfo->image_height ) {
                for ( ci = 0; ci < cinfo->num_components; ci++ ) {
                    int row;
                    for ( row = 1; row <= cinfo->max_v_samp_factor; row++ ) {
                        jcopy_sample_rows( prep->color_buf[ci], 0,
                                           prep->color_buf[ci], -row,
                                           1, cinfo->image_width );
                    }
                }
            }
            *in_row_ctr += numrows;
            prep->next_buf_row += numrows;
            prep->rows_to_go -= numrows;
        } else {
            /* Return for more data, unless we are at the bottom of the image. */
            if ( prep->rows_to_go != 0 ) {
                break;
            }
        }
        /* If at bottom of image, pad to fill the conversion buffer. */
        if ( ( prep->rows_to_go == 0 ) &&
            ( prep->next_buf_row < prep->next_buf_stop ) ) {
            for ( ci = 0; ci < cinfo->num_components; ci++ ) {
                expand_bottom_edge( prep->color_buf[ci], cinfo->image_width,
                                    prep->next_buf_row, prep->next_buf_stop );
            }
            prep->next_buf_row = prep->next_buf_stop;
        }
        /* If we've gotten enough data, downsample a row group. */
        if ( prep->next_buf_row == prep->next_buf_stop ) {
            ( *cinfo->downsample->downsample )( cinfo,
                                                prep->color_buf,
                                                (JDIMENSION) prep->this_row_group,
                                                output_buf, *out_row_group_ctr );
            ( *out_row_group_ctr )++;
            /* Advance pointers with wraparound as necessary. */
            prep->this_row_group += cinfo->max_v_samp_factor;
            if ( prep->this_row_group >= buf_height ) {
                prep->this_row_group = 0;
            }
            if ( prep->next_buf_row >= buf_height ) {
                prep->next_buf_row = 0;
            }
            prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
        }
        /* If at bottom of image, pad the output to a full iMCU height.
         * Note we assume the caller is providing a one-iMCU-height output buffer!
         */
        if ( ( prep->rows_to_go == 0 ) &&
            ( *out_row_group_ctr < out_row_groups_avail ) ) {
            for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                  ci++, compptr++ ) {
                expand_bottom_edge( output_buf[ci],
                                   compptr->width_in_blocks * DCTSIZE,
                                   (int) ( *out_row_group_ctr * compptr->v_samp_factor ),
                                   (int) ( out_row_groups_avail * compptr->v_samp_factor ) );
            }
            *out_row_group_ctr = out_row_groups_avail;
            break;      /* can exit outer loop without test */
        }
    }
}


/*
 * Create the wrapped-around downsampling input buffer needed for context mode.
 */

LOCAL void
create_context_buffer( j_compress_ptr cinfo ) {
    my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
    int rgroup_height = cinfo->max_v_samp_factor;
    int ci, i;
    jpeg_component_info * compptr;
    JSAMPARRAY true_buffer, fake_buffer;

    /* Grab enough space for fake row pointers for all the components;
     * we need five row groups' worth of pointers for each component.
     */
    fake_buffer = (JSAMPARRAY)
                  ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                               ( cinfo->num_components * 5 * rgroup_height ) *
                                               SIZEOF( JSAMPROW ) );

    for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
          ci++, compptr++ ) {
        /* Allocate the actual buffer space (3 row groups) for this component.
         * We make the buffer wide enough to allow the downsampler to edge-expand
         * horizontally within the buffer, if it so chooses.
         */
        true_buffer = ( *cinfo->mem->alloc_sarray )
                      ( (j_common_ptr) cinfo, JPOOL_IMAGE,
                       (JDIMENSION) ( ( (long) compptr->width_in_blocks * DCTSIZE *
                                       cinfo->max_h_samp_factor ) / compptr->h_samp_factor ),
                       (JDIMENSION) ( 3 * rgroup_height ) );
        /* Copy true buffer row pointers into the middle of the fake row array */
        MEMCOPY( fake_buffer + rgroup_height, true_buffer,
                3 * rgroup_height * SIZEOF( JSAMPROW ) );
        /* Fill in the above and below wraparound pointers */
        for ( i = 0; i < rgroup_height; i++ ) {
            fake_buffer[i] = true_buffer[2 * rgroup_height + i];
            fake_buffer[4 * rgroup_height + i] = true_buffer[i];
        }
        prep->color_buf[ci] = fake_buffer + rgroup_height;
        fake_buffer += 5 * rgroup_height;/* point to space for next component */
    }
}

#endif /* CONTEXT_ROWS_SUPPORTED */


/*
 * Initialize preprocessing controller.
 */

GLOBAL void
jinit_c_prep_controller( j_compress_ptr cinfo, boolean need_full_buffer ) {
    my_prep_ptr prep;
    int ci;
    jpeg_component_info * compptr;

    if ( need_full_buffer ) {/* safety check */
        ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
    }

    prep = (my_prep_ptr)
           ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                        SIZEOF( my_prep_controller ) );
    cinfo->prep = (struct jpeg_c_prep_controller *) prep;
    prep->pub.start_pass = start_pass_prep;

    /* Allocate the color conversion buffer.
     * We make the buffer wide enough to allow the downsampler to edge-expand
     * horizontally within the buffer, if it so chooses.
     */
    if ( cinfo->downsample->need_context_rows ) {
        /* Set up to provide context rows */
#ifdef CONTEXT_ROWS_SUPPORTED
        prep->pub.pre_process_data = pre_process_context;
        create_context_buffer( cinfo );
#else
        ERREXIT( cinfo, JERR_NOT_COMPILED );
#endif
    } else {
        /* No context, just make it tall enough for one row group */
        prep->pub.pre_process_data = pre_process_data;
        for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
              ci++, compptr++ ) {
            prep->color_buf[ci] = ( *cinfo->mem->alloc_sarray )
                                  ( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                   (JDIMENSION) ( ( (long) compptr->width_in_blocks * DCTSIZE *
                                                   cinfo->max_h_samp_factor ) / compptr->h_samp_factor ),
                                   (JDIMENSION) cinfo->max_v_samp_factor );
        }
    }
}
